A 3-year-old boy is brought to the emergency department after a generalised tonic-clonic seizure lasting 3 minutes associated with a temperature of 39.2 °C from an upper respiratory tract infection. He returns quickly to his normal self, neurological examination is normal and there is no meningism. This is his first seizure, and there is no family history of epilepsy. Which feature best supports the diagnosis of a simple febrile seizure?